Cluster Headache Impact Questionnaire (CHIQ) – a short measure of cluster headache related disability

Table 2 Item and factor analysis and test-retest correlation of the CHIQ

	Mean (SD)	Item difficulty	Corrected item-scale correlation (with item deleted)	Cronbach’s α (with item deleted)	Factor loading	Intraclass Correlation	95% Confidence Interval
	Mean (SD)	Item difficulty	Corrected item-scale correlation (with item deleted)	Cronbach’s α (with item deleted)	Factor loading	Intraclass Correlation	Lower Bound	Upper Bound
CHIQ1	3.37 (1.09)	67.4	0.72	0.86	0.79	0.82	0.67	0.91
CHIQ2	3.40 (1.03)	68.0	0.74	0.86	0.81	0.79	0.60	0.89
CHIQ3	3.51 (1.07)	70.2	0.66	0.86	0.71	0.81	0.65	0.90
CHIQ4	3.35 (1.01)	67.0	0.61	0.87	0.64	0.81	0.65	0.90
CHIQ5	3.19 (1.27)	63.8	0.67	0.86	0.73	0.83	0.67	0.91
CHIQ6	3.35 (1.08)	67.0	0.67	0.86	0.70	0.73	0.50	0.86
CHIQ7	1.61 (1.31)	32.2	0.53	0.88	0.56	0.91	0.83	0.95
CHIQ8	2.94 (1.25)	58.8	0.63	0.86	0.67	0.88	0.78	0.94
CHIQ score						0.91	0.83	0.95

This analysis was performed in the group of ‘active CH’ patients (n = 196). Each item showed good item analysis as well as meaningful factor loadings. Intraclass correlation coefficients (ICCs) of single CHIQ items and the CHIQ score are given

ISSN: 1129-2377